“First Light” From New Probes of the Dark Ages and Reionization Judd D. Bowman (Caltech) Hubble Fellows Symposium 2008

Redshifted 21 cm mean brightness temperature Furlanetto 2006

50 mK 0 z = 8, x i = 0.3 Data provided by A. Mesinger & S. Furlanetto Redshifted 21 cm anisotropies

CMB analogy COBE CMB Blackbody (Fundamental paradigm) WMAP (Elaborate on standard paradigm)

Complications 1.Terrestrial radio frequency interference (RFI) from TV, FM, and other transmitters 2.Ionospheric distortions of sky positions 3.Astrophysical foregrounds (dominated by Galactic synchrotron emission and extragalactic continuum sources)

Astrophysical Foregrounds Sun Galactic emission: 200 to 10,000 K (~70%) Extragalactic point sources: 30 to 70 K (~25%) Galactic radio recombination lines: < 1 K Free-free in IGM: minimal (21 cm: < 35 mK) All continuum foregrounds have spectrally smooth power-law profiles

de Oliveira-Costa et al Intensity [K] Spectral index T    Running of spectral index

Foreground Strategy Wang et al. 2006

Wolleben et al times more intense at 150 MHz Faraday rotation adds significant spectral structure Enters intensity measurement through mis-calibration 1.4 GHz polarized intensity

Pathfinder experiments under construction: GlobalAnisotropy EDGESMWA (W. Australia) CoRE (Ron Ekers)LOFAR (Neatherlands) GMRT (India) PAPER (W. Australia) Approach: Start from scratch with new instruments that exploit modern digital signal processing technology to address these challenges

EDGES Experiment to Detect the Global EOR Signature with Alan E. E. Rogers (MIT/Haystack Observatory)

Mean (Global) Brightness Temperature Furlanetto 2006 Frequency derivative Mean brightness temperature

Instrumental requirements: Do not introduce non-smooth features into the measured the spectrum Simplifications: Ionospheric distortions and polarized foreground greatly reduced for all-sky measurements

Frequency T ant

Reflections: multi-path Frequency T ant

Reflections: impedance mismatch Frequency T ant ADC LNA

Sampling artifacts Frequency T ant ADC LNA Comparison source

EDGES balun “Four-point” antenna Ground screen ADC Amplifiers and switch

EDGES “First Light” First measured spectrum partially calibrated, western Australia 1.5 sky hours Bowman et al. 2008

EDGES: Smoothness Residuals after 7 th order polynomial fit to spectrum Measured rms = 75 mK (Instrumentally limited) rms vs. integration time Black line: smoothed to 2.5 MHz Bowman et al. 2008

EDGES: Upper Limit Upper limit: T 21 < 450 mK for instantaneous reionization at z = 8 zz  T 21 z r = 8 Expected 21 cm rms  7.5 mK Bowman et al. 2008

Implications and Future Work Preliminary constraint: T 21 < 450 mK (if reionization occurred abruptly at z  8) Demonstrated viable approach First run within order of magnitude (75 mK [rms] compared to  7.5 mK) Clear path to improve performance Analog to digital converter identified as limiting component Increase bandwidth of antenna impedance match Should determine duration of reionization or constrain to: z  2 or better May be able to detect heating transition of IGM and/or exotic PBHs

MWA Murchison Widefield Array MIT, Harvard/CfA, Australian Consortium, WA government, RRI (India)

MWA The VLA in a new way… Collecting area: 8000 m 2 Spectral coverage: 80 to 300 MHz Instantaneous bandwidth: 32 MHz (z = 2) Spectral resolution: 10 kHz (40 kHz) 512 antenna “tiles” within 1.5 km diameter Field of view: 100 to 1000 deg 2 Angular resolution: 3 to 10 arcmin Sky noise dominated

MWA: Antenna Tile

+ 480 more by early 2009 The Catalog of MWA Antennae

MWA: EOR Observing Plan K Primary field: RA 60.00, Dec hours available Divided between 2 bands 6 < z < 9 Secondary field: RA , Dec , 450 hours available 6 < z < 7

8 Gpc (1000 pixels) 1 Gpc [6<z<9] (6000 channels) Zahn et al z = 7.68 x i =0.33 z = 8.16 x i =0.11 z = 6.89 x i =0.52 MWA: Data Cube

MWA: Thermal Uncertainty Bowman et al z = 6z = 8z = 10 z = 12  x i <0.1 Lidz et al. 2008

MWA: Antenna Distribution baselines 10% in tightly packed core Completely sample uv-plane within 500 wavelengths Short baselines probe both large and small spatial scales Antenna layoutBaseline distributionRotation synthesis

MWA Schedule 1/16 th collecting area installed, digital systems coming next month First engineering run: August 2008 – 100 hours on primary field w/ 32 tiles, 32 MHz – Test calibration, all-sky map, polarized sources, RRLs Complete array in early 2009 Science observing mid-2009 through 2010

Pathfinder experiments for both global and anisotropy signals are in progress to demonstrate foreground mitigation and detect signal at z > 6 Feasible and compelling near-term science goals to determine redshift (x i z<13) Summary